Chronic Kidney Disease (CKD), also known as chronic renal disease, may be a sudden or progressive loss in renal function. As the disease severity progresses, a patient with severe renal failure develops many symptoms that, if left untreated, eventually result in death. The most severe stage of CKD is End Stage Renal Disease (ESRD). ESRD, also referred to as kidney failure or renal failure, is the medical condition wherein a person's kidneys fail to sufficiently remove toxins, waste products, and excess fluid, and to maintain proper electrolyte levels.
Current treatments for CKD seek to manage comorbidities and, if possible, slow the progression of the disease. However, as the disease progresses, renal function decreases and eventually renal replacement therapy is employed to compensate for lost kidney function. Renal replacement therapy typically entails transplantation of a new kidney, or dialysis. Kidney dialysis is a medical procedure that is performed to aid or replace some of the kidney functions in severe renal failure. Hemodialysis, hemofiltration, hemodiafiltration, and peritoneal dialysis are all replacement therapies for patients who have lost most or all of their kidney function. Dialysis can remove many of the toxins and wastes that the natural kidney would remove. In addition, these therapies are used to balance the electrolyte or blood salt levels and to remove excess fluid that accumulates in patients with renal failure.
Hemodialysis treatment can be performed to remove waste products from the blood that are no longer being effectively removed by the kidneys, such as urea, creatinine and phosphates. Although the population of patients afflicted with CKD grows each year, there is no cure. The excess fluid accumulated in patients suffering from renal failure is generally removed by the ultrafiltration action of a dialysis procedure.
Hemodialysis procedures in developed countries are usually carried out three times a week in three to five hour sessions. In some geographies, hemodialysis is less available and conducted less frequently. Dialysis emulates kidney function by removing waste solutes, excess electrolytes and excess fluid from a patient's blood. During dialysis, the patient's blood that contains a high concentration of waste solutes is exposed to a semi-permeable membrane in contact with a solute-deficient dialysis solution (dialysate). Solute removal and electrolyte balancing is accomplished via diffusion across the membrane. Fluid removal is accomplished via pressure-driven convective transport through the membrane, commonly referred to as ultrafiltration. Once the blood is purified, it is then returned to the patient. Although effective at removing wastes from blood, dialysis treatments are administered intermittently and therefore do not emulate the continuous function of a natural kidney. Moreover, there are many inconveniences associated with dialysis, such as the necessity of traveling to a dialysis center and committing to time consuming treatments multiple times per week.
Although hemodialysis removes excess fluid, interdialytic intervals of a hemodialysis schedule create variations in the patient's waste removal, impurity removal, fluid removal and electrolyte balance. These variations result in patient complications and the high rates of patient morbidity and mortality. Since the mid-1990s a number of physicians have prescribed treatment regimens with increased dialysis frequency and treatment time to try to eliminate the problems associated with the thrice-weekly hemodialysis schedule. Two recent randomized controlled clinical studies have shown statistically significant benefits of a more frequent dialysis regimen. Culleton et al. (Culleton, B F et al. Effect of Frequent Nocturnal Hemodialysis vs. Conventional Hemodialysis on Left Ventricular Mass and Quality of Life. 2007 Journal of the American Medical Association 298 (11)) reported that when compared with conventional hemodialysis (trice weekly) daily nocturnal hemodialysis improved left ventricular mass (a surrogate for mortality), reduced the need for blood pressure medications and improved some measures of mineral metabolism. The FHN trial (The FHN Trial Group. In-Center Hemodialysis Six Times per Week versus Three Times per Week, New England Journal of Medicine, 2010) was a comparison of increased treatment frequency of 5.2 hemodialysis treatments a week compared with the traditional thrice-weekly regimen: “Frequent hemodialysis, as compared with conventional hemodialysis, was associated with favorable results with respect to the composite outcomes of death or change in left ventricular mass and death or change in a physical-health composite score.” Based on this data it would be desirable to have a hemodialysis system that would allow kidney patients to dialyze from five to seven days a week, if not continuously.
Despite the clinical results from the Culleton and FHN research, few patients presently undergo a higher frequency of dialysis treatment. More frequent hemodialysis is only used on a small part of the patient population due to the burden and cost of more frequent therapies. Even the thrice weekly-regime is a significant burden to ESRD patients, and an increase in treatment frequency can often be difficult due to the deficiencies in known devices and the cost of the additional treatments. Most dialysis is performed in a dialysis center; hence, there is a need for the practical implementation of more frequent hemodialysis using a simple, wearable/portable, and safe technology that can be used by a patient at home.
Typical home-dialysis equipment employs an amount of dialysis fluid greater than 20 liters, up to 120 liters or more, that must be produced by a dedicated water purification system. The typical requirement for large amounts of purified water creates a barrier in that stationary, expensive, and often architecturally incompatible water purification supply and drain systems must be connected to the plumbing.
A different water-related barrier to treatment exists in some developing regions of the world, in that infrastructure to produce the large volumes of purified water may not exist within feasible traveling distance for persons suffering from ESRD. Thus, a dialysis therapy system that does not require large volumes of purified water could increase availability of life-saving hemodialysis therapy for those suffering from ESRD in such regions. In such regions, a system that can provide dialysis therapy from just a few liters of potable or bottled drinking water is of special value. In developing regions, or even in developed regions suffering from natural disaster, a model for delivering life-saving hemodialysis therapy can be mobile dialysis units that can travel to the location where therapy is needed and provide the needed therapy. Equipment that is compact, lightweight, and free of requirements for large volumes of purified water, and not requiring a high ratio of skilled technicians per patient to operate the equipment is the equipment of choice for this therapy delivery modality.
The large volume of dialysate fluid required for dialysis is in part attributable to the large quantity of solution necessary for the diffusion of waste products removed and the balancing of electrolytes within the dialysate from the blood of a dialysis patient. Regeneration of spent dialysate is one way to reduce the total volume of a dialysis system by eliminating the need for a large reserve of fresh dialysate. However, existing technologies for regenerating spent dialysate have been met with various limitations. For example, the Recirculating Dialysate System (“REDY system”) may be subject to variations in pH and sodium concentrations that depart from physiological norms. Additionally, REDY systems have limited or no ability to remove sulfates, and may not be easily portable by the individual receiving therapy.
Development of dialysate recirculating techniques has resulted in systems that employ a variety of sorbent media, including activated carbon, urease, and zirconium-, aluminum-, and magnesium-based materials. Yet one of the problems associated with sorbent regeneration of spent dialysate is the buildup of sodium ions released as a byproduct of the adsorption process, thus necessitating a high degree of sodium concentration control which has yet to be achieved by currently available wearable or portable dialysis systems.
Some systems have attempted to address the volume and weight problems by allowing for external connections to a tap water source. However, the introduction of tap water into a dialysis system necessitates additional purification measures, thus adding to system complexity and size. As a result, such systems may not be useful for mobile or portable use.
Sorbent-based dialysate regeneration systems can be found in U.S. Pat. No. 3,669,878 Marantz et al., which describes sorbent removal of urea and ammonium ions from spent dialysate via urease, ammonium carbonate, and zirconium phosphate; U.S. Pat. No. 3,669,880 Marantz et al., which describes directing a controlled volume of dialysate through zirconium phosphate, activated carbon, and hydrated zirconium oxide columns; U.S. Pat. No. 3,850,835 Marantz et al., which describes production of a zirconium hydrous oxide ion exchange media; and U.S. Pat. No. 3,989,622 Marantz et al., which describes adsorption of urease on aluminum oxide and magnesium silicate media to convert liquid urea to ammonium carbonate.
U.S. Pat. No. 4,581,141 Ash describes removal of uremic substances from dialysate via a calcium-based cation exchanger, urease, and aliphatic carboxylic acid resin. U.S. Pat. No. 4,826,663 Alberti et al. describes a method of preparing a zirconium phosphate ion exchanger. U.S. Pat. No. 6,627,164 Wong describes production of sodium zirconium carbonate for ion exchange in renal dialysis, and U.S. Pat. No. 7,566,432 Wong describes production of zirconium phosphate particles for ion exchange in regenerative dialysis. U.S. Pat. No. 6,818,196 Wong, U.S. Pat. No. 7,736,507 Wong, U.S. Application Publication 2002/0112609 Wong, U.S. Application Publication 2010/0078387 Wong, and U.S. Application Publication 2010/00784330 Wong, describe cartridges for purification of dialysis solutions using sodium zirconium carbonate.
U.S. Pat. No. 6,878,283 Thompson, U.S. Pat. No. 7,776,210 Rosenbaum et al., U.S. Application Publication 2010/0326911 Rosenbaum et al., U.S. Application Publication 2010/0078381 Merchant, U.S. Application Publication 2009/0127193 Updyke et al. and U.S. Application Publication 2011/0017665 Updyke et al. describe filter cartridges having a plurality of types of filter media including zirconium compounds, urease, and alumina for dialysis systems. WO 2009/157877 A1 describes a urease material having urease immobilized on a substrate intermixed with a cation exchange material or zirconium phosphate material to improve workability for the reduction of clogging and to improve absorption of ammonium ions generated by the urease.
Management of impurities in regenerated dialysate can be found in U.S. Pat. No. 4,460,555 Thompson and U.S. Pat. No. 4,650,587 Polak et al., which describes magnesium phosphate media for removal of ammonia from aqueous solutions, U.S. Application Publication 2009/0282980 Gura et al.; “A Study on the Temperature Variation of Rise Velocity for Large Clean Bubbles,” Leifer et al., J. Atmospheric & Oceanic Tech., Vol. 17, pp 1392-1402; “Terminal Velocity of a Bubble Rise in a Liquid Column,” Talaia, World Acad. of Sci., Engineering & Tech., Vol. 28, pp. 264-68; U.S. patent application Ser. No. 12/937,928 to Beck; U.S. Pat. No. 5,468,388 to Goddard et al.; U.S. patent application Ser. No. 12/182,489 to Kirsch; U.S. patent application Ser. No. 12/355,128 to Gura et al.; U.S. Pat. No. 4,371,385 to Johnson; U.S. Pat. No. 4,381,999 to Boucher et al.; U.S. patent application Ser. No. 12/516,786 to Wallenborg et al.; U.S. Pat. No. 4,828,693 to Lindsay et al.; U.S. Pat. No. 5,762,782 to Kenley et al.; U.S. Pat. No. 7,981,082 to Wang et al.; and U.S. patent application Ser. No. 13/100,847 to Palmer.
There is a need for systems and/or methods that can simplify and automate these tasks for those individuals suffering from ESRD who are unable to access a dialysis centers, or who prefer not to. There is also a further need for expansion of hemodialysis therapy to individuals, or those living in developing regions where there is limited space available for the equipment at the home including those individuals suffering from ESRD who live in a single room shared by multiple individuals.
In particular, there is a need to provide a system including a degas module for removing unwanted gas molecules from a circulating fluid before, during, and/or after a hemodialysis process.